This is what Nagayu says about their product:
The Nagayu spa system is delivered to your dog during the final rinse period. It looks like a large tablet and this is added to the final rinse water.
Nagayu sell a shower head into which a puck can be inserted giving a three minute treatment which you can do at home. However, As Centre Stage uses a recirculating bathing system, the puck is added to the water and continuously circulated over your dog giving a much longer and more thorough CO2 treatment.
As the puck comes into contact with water it starts to fizz (a bit like a bath bomb) and generates millions of carbonic acid and hydrogen ions which transform the water into to a CO2 SPA. While showering with the CO2 SPA, the CO2 enters the blood vessels causing them to expand; this in turn increases the blood flow. Thus cells receive more nutrients and oxygen, resulting in a boosted metabolism which speeds up the healing process.
Nagayu CO2 SPA is able to decompose the body fluid that causes odor and give a much better cleaning than regular water. At the same time, the effect of the bicarbonate and hydrogen ions also wash off mineral waste and silicon dirt clogged in the hair root. This results in a full, silky, and healthy coat.